1. Field of the Invention
The invention relates to a transfer drive for a press that preferably has a three-axis transport of workpieces through machining stations.
2. Discussion of the Related Art
A conventional transport device for transporting parts in a transfer press comprises two gripper rails which extend in the transport direction of the parts and, in addition to the longitudinal and lifting movements, carry out an additional transverse movement, gripper elements being provided on the gripper rails themselves. In order that the transport elements do not interfere within the tool space during the machining operation of the press, the gripper rails in the three-dimensional transfer system have to be moved laterally out of the tool space again.
DE 38 42 182 C1 has disclosed a gripper-rail drive for transfer presses, in which the gripper rails execute a three-dimensional traveling movement. In particular, in addition to the conventional longitudinal movement and lifting movement of the two gripper rails extending in parallel, provision is made for an additional transverse movement as a clamping or closing movement for gripping or clamping the workpieces. For this purpose, each gripper rail is hinge-mounted via a push rod on a carriage which can be displaced transversely, in order to adapt to the respective workpiece size. The respective closing movement of the gripper rail is then carried out as a lateral pivoting movement on a carriage which is stationary in the transverse direction, by means of appropriate ball joints. In order to carry out the advancing, clamping and lifting movement of the carrying rails, provision is made for conventional cam disks over which cam-follower levers travel, the drive to the gearbox being provided by the press head. A basic illustration of such a drive or a pair of gripper rails is also reproduced in EP 0 210 745 A2 (FIG. 4).
In addition, DE 39 13 663 A1 has disclosed a transposing device for a transfer press, in which the drive for trolleys in the parts transport direction is provided by a cam-follower lever arrangement. The lifting movement of the running rail is provided via the drive of a cam-follower lever, whose movement is transmitted to the running rail via a longitudinal rod and a deflection device.
The drawback with this conventional art is the fact that the three-dimensional movements have to be assisted by guides which are complicated and sensitive to dirt for the individual movement elements, and make complicated protective coverings necessary. In the case of rough operating conditions with a high accumulation of dirt, such as is the case, for example, in forging presses, the guides for the individual movements are very highly stressed, and functional faults are unavoidable as a result, for example, of grooves or the so-called xe2x80x9cfrettingxe2x80x9d of the guide surfaces. It is particularly disadvantageous if the guides are arranged in the area of the transport plane or even underneath the transport plane.
The claimed invention is based on the object of providing a transfer drive which, to the greatest possible extent, dispenses with guides which are sensitive to dirt for the individual movement elements.
This object is achieved by the features of the claimed invention.
Advantageous and expedient developments of the transfer drive claimed in Patent Claim 1 are specified in the subclaims.
The claimed invention is based on the knowledge that a transfer drive that is used under rough production conditions must manage as far as possible without guides which are sensitive to dirt for the individual movement elements. Using this knowledge, the claimed invention proposes a transfer drive which comprises movable hinged rods in a suspended arrangement, as a result of which a type of xe2x80x9cfloating mountingxe2x80x9d without additional guides is achieved. In particular, as a result of the use of a three-dimensional drive, a type of xe2x80x9cmulti-point suspensionxe2x80x9d is provided, which means that the gripper rails are suspended in a defined way on hinges in all three axes of movement, so that it is possible to dispense with conventional guides because of their sensitivity to dirt. At the same time, it is advantageous that all the hinged rods and push rods are arranged above the transport plane of the parts, so that the transport space located underneath can be equipped without any guides which can become dirty for the transfer drive. Accordingly, the transfer drive is equipped with hinged rods or push rods and levers for all movements of the gripper rails in all three directions of movement, since these items of equipment are connected to one another via rotary joints, which can be sealed off much better against dirt than conventional linear guides. In particular for use in a forging company, the arrangement of the transfer above the transport plane is advantageous, that is to say the dirt which accumulates at the bottom cannot hamper the transfer drive.
A further significant advantage of this arrangement consists in the good accessibility of the working space, for example for the spraying system of the mold engraving or in the event of a die change.
Further details and advantages of the claimed invention emerge from the following description of exemplary embodiments in conjunction with the drawings.